This invention relates to multicell sealed lead-acid batteries of the recombinant type and particularly to vibration-resistance intercell connections in recombinant type lead-acid batteries.
Multicell batteries employ intercell connections to series connect the individual cells together to achieve the desired battery voltage. The intercell connections are typically constructed to be leak tight, which prevents electrolyte spillage and electrolyte bridging between cells. Three types of intercell connections used with flooded batteries are external, over-the-wall, and through-the-wall. With the external type, the leads are brought through the individual covers of the cell of each cell via individual sealing means. The intercell connections are made over the individual covers. With the over-the-wall type, the leads are brought up to a notch in the intercell wall and connected. The batteries are then inverted, and lowered onto the cover, which contains a sealing material such as epoxy which seals below the level of the notch. With through-the-wall connections the leads are brought up to a hole in the intercell partition, and welded through the hole to make a sealed connection. Lead-acid batteries of this type typically employ an L-shaped lug burned or cast onto the individual electrode tabs. Examples of vibration-resistant through-the-wall intercell connections in recombinant type lead-acid batteries are found in U.S. Pat. No. 4,495,259 (Uba) and U.S. Pat. No. 4,521,498 (Juergens).
Recombinant batteries, that is lead-acid batteries that rely on oxygen recombination during overcharge to suppress water loss through electrolysis, may employ any of the aforementioned types of intercell connections. However, since recombinant batteries do not have free flowing electrolyte, intercell connections have been proposed which do not make a sealed connection across the intercell partition. U.S. Pat. No. 4,383,011 (McClelland, et al.) illustrates in FIG. 9 thereof a unitary strap and intercell connector which bridges across a cell partition and is contained within the common gas or head space of the battery. Similar intercell connection arrangements are disclosed in U.S. Pat. Nos. 4,399,607 (May) and 4,424,264 (McGuire, et al.). The May patent further discloses a process by which the combination strap and intercell connector are formed, namely by inverting the battery container and forming the combination plate straps and intercell connectors by dipping the plate tabs into mold cavities into which has been introduced molten lead. Recombinant batteries utilizing the aforementioned combination strap/intercell connectors have proved less than satisfactory in applications where significant vibrational forces are present, e.g. in automotive and aircraft applications.
European Application No. 0 220 062 Al (Morrall) also discloses a combination strap and intercell connector, which passes through an aperture in an associated intercell partition. A U-shaped sealing member engages the intercell partition and the sides and tops of the intercell connector, providing some vibration resistance, however support is confined to the area where the intercell connector passes through the partition. The top of the intercell connector is spaced substantially from the lid of the battery. Japanese Patent Application No. 56-119471 (Jinushi), filed July 29, 1981 discloses a similar unitary strap and intercell connector supported by a U-shaped clip at the partition, and spaced from the undersurface of the lid.
U.K. Patent Application GB No. 2061604 A discloses a combination strap and intercell connector which is formed by casting a metal bar in a mold formed integrally with the intercell partition and being open at its bottom so as to rest directly on the fibrous separator mat extending beyond the electrode plates. The obvious drawback of this construction is that the resultant cast strap/intercell connector will be resting directly on the electrolyte wetted separator, which will lead to a direct electrolyte bridging path between adjacent cells in turn causing local action and self-discharge. Moreover, the close proximity of the underside of the cast strap to the top of the electrode plates can lead to short-circuiting as the positive electrode plates grow during cycling, penetrate the separator layer, and come into contact with the negative polarity portion of the cast strap.
An object of this invention is to provide a vibration-resistant multicell lead-acid battery employing a combination unitary strap and intercell connector providing a low-profile connection for maximum utilization of interior battery compartment space for active materials. It is a further object to provide such a low profile, vibration-resistant construction while inhibiting the formation of intercell electrolyte bridging paths, and the creation of short circuits during cycling. It is a further object to provide the foregoing construction by a simple process lending itself to mechanized assembly techniques.